The Reproductive and Developmental Biology Training Program at the Massachusetts General Hospital (MGH) provides its trainees with an intensive research experience in basic and/or clinical investigation under the attentive mentorship of a skilled faculty and complemented by a strong didactic program underpinning the sciences of reproductive and developmental biology. Trainees are selected from a highly talented applicant pool of M.D.s, M.D./Ph.D.s, or Ph.D.s on the basis of their prior academic and/or research accomplishments, a strong future commitment to an academic career in biomedical investigation, and a personal interview indicating their proper motivation and future potential. The PI (Dr. William F. Crowley) is a Professor of Medicine at Harvard Medical School and the Director of two NIH-funded Centers. He is an established senior scientist and recognized mentor who shares the governance of this Program with an experienced committee of senior faculty members (Drs. Patricia Donahoe, Joel Habener, and Janet Hall) that serve as Co-Directors. The total training faculty consists of 13 active, well-funded scientists whose diverse expertise and investigative interests line a spectrum of reproductive and developmental research from fundamental developmental biology to bench-to-bedside translational clinical investigations. Trainees are closely supervised by an active and individualized mentorship program overseen by the senior faculty and are encouraged to interact extensively with junior faculty who typically serve as in a co-mentorship role. An extensive program of rigorous didactic sessions interlaces tightly with individually strong, independent laboratory programs that remain at the heart of the trainees' program and complements their 2-3 years of research experience. Typically, the training period involves several additional years as junior faculty that permits the consolidation of skills required for maximal competitiveness for subsequent independent support, the ultimate goal of this Training Program. Research facilities (27,000 square ft) are fully-equipped and recently modernized laboratories are dedicated to the training faculty. The institutional investigators are highly funded by the NIH, the environment is superb, and reinforcement from two NIH Reproductive Sciences Centers' programs is substantial. The track record of past trainees indicates substantial leadership in reproduction. Thus, this training grant represents a critical stabilizing element in all of these individual research programs and is thus a crucial link that enables talented trainees to achieve subsequent independent careers in Reproduction and Developmental Biology through stable funding, mentored research projects, and a rich didactic program.